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Protein interactions with surfactants are dependent on their physiochemical properties. The effect of cationic gemini surfactant hexanediyl-a,u-bis-(N-(2-hydroxyethyl)-N-methylhexadecylammonium dibromide) on the stability and activity of hen egg white lysozyme was compared with its monomeric counterpart N-(2-hyroxyethyl)-N,N-dimethylhexadecylammonium bromide at pre and post micellar concentrations. This study utilizes circular dichroism (CD), steady-state fluorescence spectroscopy, extrinsic fluorescence spectroscopy, time-resolved fluorescence spectroscopy, UV-visible spectroscopy, molecular docking and turbidity assays to resolve the conformational stability and antibacterial activity of lysozyme in the presence of surfactants. Micelles of both cationic surfactants were observed to stabilize the conformation of the protein, however, gemini was found to stabilize it in a much higher micellar concentration range. Detailed analysis of the time-resolved fluorescence spectroscopy results suggests contribution of the lifetime values of Trp62 and Trp108 to the overall conformation change of lysozyme with the increase in concentration of the respective surfactants, which is further correlated with the steady-state fluorescence and CD spectroscopy results. Furthermore, from the CD analysis it was found that the cationic single chain surfactant strongly perturbs the secondary and tertiary structure of the protein as compared to the gemini surfactant. Through docking results, it was found that the gemini surfactant binds weakly with lysozyme as compared to the single chain surfactant. Specifically, the antibacterial activity of lysozyme was found to be increased in the presence of cationic gemini surfactant, which extrapolates the use of these surfactants in pharmaceutics and industries. Scheme 1 Structure of N-(2-hydroxyethyl)-N,N-dimethylhexadecyl ammonium bromide (M 16 ) and hexanediyl-a,u-bis-N-(2-hydroxyethyl)-N-methylhexadecyl ammonium dibromide (G 16 ). Scheme 2 Scheme showing the interaction pattern of M 16 and G 16 with lysozyme before and after CMC.

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Objective:Viva voce examination is an important tool of evaluation in medical examinations marred by high subjectivity. Gross subjectivity in viva voce assessment can be reduced by structuring it.Materials and Methods:The marks obtained in theory and viva voce (traditional viva voce examination [TVVE]) of I sessional, II MBBS students were compared and a huge disparity was identified. A structured viva voce examination (SVVE) was then proposed and experimented as an objective and standardized alternative. Sets of equitable question cards for SVVE were prepared, each having eight questions with two parts each, arranged successively with increasing difficulty, domains of learning, and appropriate marks. The percentage variation in scoring in viva versus theory marks was calculated for both TVVE and SVVE, and students were grouped as Group I (+100 to +51%); Group II (+50 to −50%); Group III (−51 to −100%); Group IV (−101 to −150%); Group V (−151 to −200%); and Group VI (< −200%) variation, as? inappropriate, appropriate, inappropriate, erroneous, more erroneous and most erroneous respectively. Student’s feedback on the SVVE was also obtained.Results:In TVVE (n = 128), the students distributed were:none,17.2%, 23.4%, 22.7%, 11.7% and 25% in Group I, II, III, IV, V, and VI in contrast to SVVE (n = 107) as 7.5%, 57.9%, 19.6%, 6.5%, 5.6%, and 2.8%, respectively. Marked disparity of TVVE was annulled with SVVE. Student’s feedback was quite encouraging with 83% overall acceptability and almost 66% preferred SVVE.Conclusion:SVVE was more realistic as compared to TVVE. Most of the students favored this approach.

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